【安卓开发】单例模式解决Broadcast广播重复接收

最近在写一个音乐类APP时需要从Notification发送广播给Service执行操作，但是在BroadcaseReceiver中出现onReceive()被多次调用的问题。网上搜索了很久都没找到解决方案，但也在搜索过程中收到了一些启发，于是决定把广播接收器变成单例模式，没想到效果一级棒。

/**
 * 广播接收器部分，单例模式
 */
class NotificationReceiver private constructor() :
            BroadcastReceiver() {

        companion object {
            const val PREVIOUS = "previous"

            const val PAUSE = "pause"

            const val PLAY = "play"

            const val NEXT = "next"

            val default = NotificationReceiver()
        }

        private var weakReference: WeakReference? = null

        override fun onReceive(context: Context?, intent: Intent?) {
            Log.d(TAG, "收到广播了，intentAction：${intent?.action}")
            when (intent?.action) {
                PREVIOUS -> {
                    weakReference?.get()?.previous()
                }
                PLAY -> {
                    weakReference?.get()?.play(false)
                }
                NEXT -> {
                    weakReference?.get()?.next()
                }
                PAUSE -> {
                    weakReference?.get()?.pause()
                }
            }
        }

        fun setWeakReference(weakReference: WeakReference) {
            this.weakReference = weakReference
        }

    }

下面的MyMediaSession类用于演示注册广播

private class MyMediaSession(private val mContext: Context) {
    ......
    private var receiver : NotificationReceiver? = null
    ....
    // 在实例化时就把广播注册了
    init {
        // 注册广播
        if (receiver == null) {
            receiver = NotificationReceiver.default
            val filter = IntentFilter()
            filter.addAction(NotificationReceiver.PAUSE)
            filter.addAction(NotificationReceiver.PLAY)
            filter.addAction(NotificationReceiver.PREVIOUS)
            filter.addAction(NotificationReceiver.NEXT)
            mContext.registerReceiver(receiver, filter)
         }
     }
    ....
    private fun unregister() {
        mContext.unregisterReceiver(receiver)
    }
    ....
}

这样就只能获取到一个广播接收器实例，加上receiver == null 的判断确保只注册一次